Oral allergy syndrome

What is oral allergy syndrome?

If you are suffering from oral allergy syndrome (OAS) then your mouth and throat react to certain foods you may eat. This is because the foods contain similar or the same proteins to something you are allergic to. The immune system therefore has had a hard time distinguishing between them. Oral allergy syndrome, also called pollen-food syndrome, is especially common among people suffering from hay fever and who might be hypersensitive to apples, nuts and stone fruits for example. For people with hay fever, the oral allergy syndrome is usually worse during the hay fever season and some even have to avoid certain foods at that time.

Oral allergy syndrome is also triggered by certain foods within certain food groups. This implies that a person who is allergic to a specific kind of stone fruit, like peach, will probably also react to apricot, cherries and plums. Not all allergic people suffer from oral allergy syndrome but if you are one of them you should pay attention when you are shopping for food, especially since ready-made food might contain hidden allergens. Be sure to keep your allergy tablets to hand in case of problems and do not be afraid to talk to your doctor in case your medicine is not helping you. This might mean you need to try something else.

Symptoms of oral allergy syndrome

Common problems from oral allergy syndrome are swollen lips that might itch and sting and itchiness of your throat and mouth when you are eating an apple or nuts for example. Around half of all people who are allergic to birch, hazel and alder pollens will experience mild symptoms such as itchiness of the mouth as they are eating hazelnuts. Many react in the same way when eating almonds, raw potatoes, raw carrots and raw apples. This is because those foods contain the same protein as pollen. Oral allergy syndrome may also lead to problems with your stomach and intestinal tract like nausea, vomiting and diarrhoea. Sometimes hives or a nettle rash appear, along with sneezing and runny, itchy eyes.

Different types of oral allergy syndromes

Often people allergic to birch pollen will also be affected by pollen food syndrome. Allergy to mugwort pollen may also produce strong reactions to some foods. However in people allergic to grass pollen, oral allergy syndrome is unusual. Cross reactions sometimes occur among people allergic to natural latex, especially among health care professionals and cleaning staff who use rubber gloves. It is usually manifested as eczema on the part of the skin that has been in contact with latex but itch of the mouth, breathing difficulties and gastro-intestinal problems may also occur.

Allergic to:

Cross-reacts with:


Stone fruit (plums, cherries, apricot, peaches, nectarine, almonds), apple, pear, nuts (walnuts, hazel nuts, para nuts, kiwi, celery, root vegetables (carrot, potato skin), strawberries


Peanuts, soy beans, peas, tomatoes, onion




Celery, parsley, carrots, garlic, bell pepper, fennel, banana, melon, some herbs, chamomile, sunflower seeds, nutmeg

Dust mites




Banana, avocado, chestnuts, nectarines, plums, cherries, peanuts, shell fish, tomatoes

Chicken feathers


Eggs, chicken meat


If you are suffering from birch pollen allergy, it may still be possible for you to eat the cross-reacting fruits or vegetables if boiled or preserved, since the allergen will have been altered. However, it should be noted that the same does apply for almonds, nuts or peanuts. For those allergic to mugwort and grass, cooking the foods will not help.

Oral allergy syndrome treatment

To begin with, you should avoid eating the foods you are cross-reacting to. This is of special importance during pollen season and if you are a very sensitive allergic person. Read the table of contents attentively, because nuts and seeds will sometimes appear where you least expect them. If you suffer from a pollen allergy, it is important to treat it with effective medicines since medicines will work more effectively the sooner the treatment is started.

The treatment that will suit you the best depends on your allergy symptoms. If your nose is causing you the most problems you may try a nasal spray with antihistamines or cromoglycate. Symptoms affecting your eyes are usually treated with hay fever eye drops, and if your problems are hitting both eyes and nose, tablets or a combined nasal spray containing antihistamine are most often effective. These medicines may be bought over-the-counter in pharmacies and can, if needed, be combined.

If you are not feeling better after having medicated yourself with over-the-counter medicines within two weeks you will need to contact a doctor.  You should also consult your doctor if symptoms are troublesome, who may prescribe a medication or suggest an allergy test. 

UK/GEN/15/0057c                         Date of preparation: December 2015 

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